Storage tanks are widely used for storing a variety of liquids. Some of these liquids are hazardous and can be corrosive and/or flammable. In particular, underground storage tanks are used extensively for the storage of liquid gasoline at retail gasoline stations. Filling of the tanks is accomplished from a transport tank truck parked adjacent the top of a fill pipe located at ground level. The fill pipe is permanently connected to the underground storage tank. The transport tank truck operator attaches a flexible delivery hose leading from the transport tank truck's control panel to a liquid tight fitting on the top end of the tank's fill pipe. The operator next opens a valve located at the transport tank truck. Gasoline fills the flexible hose, the underground tank's fill pipe and finally the storage tank.
The filling operation is normally accomplished by gravity unloading of the gasoline in the transport tank truck to the underground tank. The gasoline flows into the underground storage tank until the filling operation is stopped by the tank truck operator or the underground tank and access pipes completely fill creating an overfill situation. Such overfill results in a substantial amount (up to about thirty-five gallons) of gasoline trapped in the commonly used four inch diameter flexible delivery hose. When an overfill occurs the operator first turns off the valve at the transport tank trunk. Unless special precautions are taken, gasoline contained within the flexible delivery hose is spilled onto the ground causing earth and water contamination.
Present underground tanks are required by federal regulations to have an overfill containment device to prevent overfilling. Various overfill devices and auxiliary holding tank systems are known in the prior art. Examples of these are disclosed in U.S. Pat. Nos. 3,983,913; 4,204,564; and 4,501,305. The disclosed systems are not fully satisfactory in one way or another.
There has now been discovered a storage tank system with provision for overfilled liquid. The present invention solves the problems inherent with existing storage tank systems and auxiliary overfill equipment.